tuning with a pulley

[kirks5oh]

i recently asked this same basic question at one of the other forums and i just wanted to get everyone's input. when adding a pulley (2.93) to your car, i was under the impression that most owners simply plugged in their pulley-specific chip or downloaded to the car's computer (using the diablosport tuner for example) the correct timing/fuel curves for the added boost. has everyone who's added a smaller pulley tuned their car using a dyno? how many have added a pulley without a professional dyno tune session to set their timing/fuel curves?
thanks

[93KingCobra]

I would do it NO MATER WHAT...That motor is too expensive to play with. Get the proper tune by a professional you wont regret it for the amount of money a couple pull's will cost you..IMO

[Butcher]

Originally Posted by 03KingCobra

I would do it NO MATER WHAT...That motor is too expensive to play with. Get the proper tune by a professional you wont regret it for the amount of money a couple pull's will cost you..IMO

I agree completely. You used the DiabloSport as an example. I used one for a week, then chucked it for an SCT. I found the Predator tuned it on the lean side, and for daily driving, that would be I guess, ok. But honestly, who doesn't put their foot in it? The Predator ran it too lean imo...a good tune on the dyno is the best way to ensure reliability, even if it does tune it down a tad.

Jimmie

[cobra2112]

What kind of Air to Fuel #'s are considered to lean? I had a Predator tune done with a dyno check and my tech said it was running on the safe side. Just wondering what your results where?

[gnxs]

Originally Posted by cobra2112

What kind of Air to Fuel #'s are considered to lean? I had a Predator tune done with a dyno check and my tech said it was running on the safe side. Just wondering what your results where?

I like to be under 12:1 myself (preferably 11.8 or so), but others are above that (low 12s) with no problems. Here's my 2.76 pulley/K&N FIPK/Bassani chart:

http://mywebpages.comcast.net/gnxs/I...no_8-19-04.jpg

With the canned predator tune, the car was lean at low RPMS and WAY rich (off the chart - less than 10:1) up top.

The above pull was made on a tune from James at RWTD. This was the base tune he sent me. I didn't bother getting it tweaked since there's a Whipple going on the car now, but if I did want it tweaked I'd have had him lean it out ever so slightly from 5,500-6,500 rpms.

DON'T CHANGE THE PULLEY WITHOUT GETTING TO A DYNO OR GETTING A WIDEBAND ON THE CAR VERY QUICKLY! These motors are too expensive to get cheap with and a custom tune will probably net you another 20-30 hp over the canned tune that comes with the flasher.

[kirks5oh]

so assuming i get a custom tune from a dyno session, would i still use the predator tuner program? does this tuner allow you to set a/f ratios at each engine rpm? i assume that's what is meant by a custom tune. what about timing? does this have to be set at each rpm? does anyone know of a reputable dyno shop in the columbus ohio area? thanks for all the help!

[gnxs]

Originally Posted by kirks5oh

so assuming i get a custom tune from a dyno session, would i still use the predator tuner program? does this tuner allow you to set a/f ratios at each engine rpm? i assume that's what is meant by a custom tune. what about timing? does this have to be set at each rpm? does anyone know of a reputable dyno shop in the columbus ohio area? thanks for all the help!

Some shops use SCT software and some use Diablo (Predator) software. You can have a shop build you a custom tune from dyno sessions that could be loaded into your predator. However, the Predator (and SCT flash tuner) only has limited control from that point. Minor tuning changes need to be done by a tuner unless you have a stand-lone system (like a F.A.S.T.) or the SCT Pro-Racer Package.

If you want to keep using the Predator, you need to use a tuner that uses Diablo software to tune. I don't know of any in your area offhand, but it sounds like your mods are pretty basic. I'd call RWTD. I'm sure the tune he provides will be VERY close to optimum for your car.

My $0.02.

[cobra2112]

The Predator that I have will allow you to make changes to air/fuel from 2k-4k rpm and 4k-to redline. It will allow you only to adjust the overall percentage of that particular rpm range. Ignition timing can also be adjusted but I didn't look into it at all yet. Diablosport's website will allow you to download the manual to see exactly what it does. Good Luck! Let us know how you make out with whatever way you decide to go.

[kirks5oh]

thanks for all the replies guys, i've contacted a dyno center in my area (columbus, ohio) that frequently tunes cobras, and they noted some of the problems mentioned about the diablosport. they burn custom chips with their dyno tunes.
all this is tempting, i love the car's power right now, but i know i will love it with more power. i don't want to break anything at all, let alone on a car with under 3,000 miles on it. at least i've heard of some guys with these diablosport tuners and pulleys who break things swapping out the pulley and reprogramming the stock tune for the dealer, but its impossible to hide the fact that a chip has been added right? am i being too paranoid?

[gnxs]

Originally Posted by cobra2112

The Predator that I have will allow you to make changes to air/fuel from 2k-4k rpm and 4k-to redline. It will allow you only to adjust the overall percentage of that particular rpm range. Ignition timing can also be adjusted but I didn't look into it at all yet. Diablosport's website will allow you to download the manual to see exactly what it does. Good Luck! Let us know how you make out with whatever way you decide to go.

The changes the Predator (I own one) allow for timing are only at two load points within the two rpms ranges you mentioned. Not sure if the fuel is the same way, but changes you make with the predator affect VERY broad rpm ranges. Fine tuning invididual load and rpm points must be done by a tuner with the correct software.